Disposable absorbent articles like baby diapers or adult incontinent briefs are well-known in the art and commercially sold on a broad scale. Many of the commercially available diapers or briefs comprise an adhesive tape fastening system to secure the articles on a baby or an incontinent adult. The performance of the fastening system represents a key element for the functionality of such articles and therefore contributes to the commercial success of absorbent articles incorporating adhesive tape fastening systems.
This fact is reflected in the vast amount of references concerned with disposable absorbent articles having adhesive fastening systems. In particular, adhesive fastening systems which allow the absorbent article to be opened and reclosed in order to check whether a change is indicated, often referred to as "refastenable" systems, have found much attention in the art.
The design of adhesive fastening systems for disposable absorbent articles concentrates on two major criteria which are generally opposed to each other: adhesive bond security and refastenability. It is the goal of such adhesive fastening systems to achieve both strong adhesive bond security (a bond which remains adhered during use) and non-destructive removal of the tapes for refastenability. It has generally been believed that the peel force of a pressure-sensitive adhesive tape from a substrate is one of the most important factors in determining how an adhesive fastening system actually performs during use. The peel force property shows that higher peel forces improve the bond security of the fastening system while also making it more difficult to remove without tearing the landing member. Thus, early solutions to providing an improved adhesive fastening system focused on balancing the peel force in order to optimize bond security and refastenability. One focus area was on adjusting the properties of the elements of the adhesive fastening system. Particularly, the tensile strength (tear resistance) of the landing member, typically the unreinforced backsheet of the absorbent article, was increased so that the backsheet could withstand high tensile stresses caused by the tape removal. However, such backsheets tended to be rigid, noisy, expensive and more burdensome on material resources and the environment (require more materials). Conversely, the tape properties were adjusted to increase contact area and lower peel force so as to not exceed the strength of the backsheet. These systems were expensive, inconvenient and had low bond security at low application pressure. As the demand was made for high bond security adhesive fastening systems to meet the in-use conditions placed upon absorbent articles, additional strength had to be added to the backsheet to avoid its tearing. This additional strength was added to the backsheet by increasing its thickness, and/or by reinforcing it such as by laminating additional materials to the inside or outside of the backsheet in the fastening area.
For example, U.S. Pat. Nos. 3,875,621 and 3,931,666 each disclose adhesive tapes for diapers that provide refastenability by transferring a target tape to the backsheet thus preventing destruction of the backsheet when detaching the tape and providing a target surface for refastening it. In U.S. Pat. Nos. 3,950,824, 4,067,337, and 4,769,283 refastenability is approached by providing particular adhesive surfaces, selecting particular adhesive materials, subdividing the adhesive surface into small areas or using different adhesive materials on different portions of the adhesive tape surface. These approaches to refastenability resulted in additional cost and complexity when manufacturing the articles and some also made usage of the articles by consumers more complex.
U.S. Pat. Nos. 4,237,889, 4,389,212 and 4,769,283 disclose improved tape backing materials and tape backing designs. These improvements attempt to reduce tape backing failure by providing cross-directional elasticity or improved flexibility and softness of the tape backing material.
U.S. Pat. Nos. 3,867,940, 4,296,750 and 4,983,174 are directed towards reinforcing the backsheet in order to prevent tearing of the backsheet upon opening of the adhesive fastening system. In particular, a coating of a hot melt adhesive on the backsheet as well as application of an additional layer of film material to reinforce the backsheet were disclosed and have found wide use, especially on baby diapers. This solution provides simplified refastenable adhesive tape fastening systems for the user over the target tape type of fastening systems since a single piece refastenable tape of high adhesive strength can be used without destroying the backsheet material. However, these systems increase the manufacturing complexity, the cost of the article and the environmental burden upon disposal of articles containing the extra reinforcement materials.
U.S. Pat. Nos. 4,655,761, 4,743,242 and 4,880,422 appear to address part of the above problems with reinforcing systems by providing backsheets capable of accepting adhesive tapes without reinforcement areas. These references focus on strengthening the backsheet material by selecting particular polymer film material compositions or embossing patterns. However, in order to maintain the prime function of the adhesive tape, namely to securely adhere to the backsheet of the disposable article, these systems require high tape peel force values, thereby compromising refastenability of the tape with the enhanced probability of destroying the backsheet. Further, the problem of bond security is aggravated by "deep embossing" (i.e., more than 50 microns) of the backsheet which reduces the available adhesive contact area.
U.S. Pat. Nos. 4,540,415 and 4,728,325 disclose special adhesive compositions or polymer film compositions for backsheets to provide refastenability. However, their technical, economical and/or ecological performance have heretofore not resulted in commercial availability of low cost refastenable adhesive tape fastening systems.
In general, all adhesive fastening systems for disposable absorbent articles have sought to balance the competing technical demands of refastenability, contamination sensitivity, initial adherence and long term bond strength with economical, ecological and convenience requirements. However, none of the commercially available adhesive fastening systems is currently able to meet all demands and requirements. The essential technical performance of adhesive tape fastening systems has been provided by systems employing aggressive adhesive tapes on backsheets with expensive reinforcement areas or multi-layer adhesive tape systems with transferable target tapes which have low consumer acceptance due to their complexity. These systems are especially unsuitable for incontinent briefs where the cost of such complex systems are much greater since the briefs are much larger and the range of the physical dimensions of the wearer is greater requiring larger area landing members to provide adjustability. Further, recent environmental concerns have dictated the use of less material. However, simple, low cost and low material consumption adhesive fastening systems are not available without compromising bond security or refastenability.
Therefore, an object of the present invention is to provide an adhesive fastening system having the essential technical bond security and fastening performance while providing refastenability without tearing of the landing member.
A further object of the present invention is to reduce or maintain the amount of materials used in the construction of the adhesive fastening system thereby providing ecologically and economically acceptable disposable absorbent articles.
A still further object of the present invention is to provide superior bond security and superior refastenability when the landing member is a reinforced backsheet.
An additional object of the present invention is to provide disposable absorbent articles with a low cost, refastenable, adhesive fastening system by using only the low caliper backsheet as the landing member.
Yet another object of the present invention is to provide a disposable incontinent brief or baby diaper using the refastenable adhesive tape fastening systems according to the present invention.
These and other objects of the present invention will be more readily apparent when considered in reference to the following description and when taken in connection with the accompanying drawings.